When a user attempts to archive an entire folder within their Inbox, the user receives the following warning, but only if there are no messages in the root of the folder that they are attempting to archive.
"You cannot archive an entire mailbox in Enterprise Vault"
Mailbox
..Inbox
....Old Messages <-- attempt to archive this folder, no messages here
......From Bob <-- may or may not contain messages
......From Tim <-- may or may not contain messages
In other words, they only way they can archive the Old Messages folder is at least one message at the root of this folder.
Outlook 2003, happens with both SP1 and SP2
EV 6.0 SP2 on W2k3 w/ SP1